Method and apparatus for logging drill holes



u 3 .L. DILL ON 2,425,86

us'rabn AND arrm'rus FOR Loeema-nniu. HOLES 2a, 1936 2 Sheets-Sheet 1Original Filed Aug.

i f; aehc I ATTORN EY.

Aug. 19, 1941- DILLON, 2,425,859

usrnon AND APPARATUS FOR poeemo mum. news I ori inal Filed Aug. 2a. 19362 Shets-Sheet 2 1420M, INVENTOR.

' ATTORNEY.

Patented Aug. 19, 1947 METHOD AND APPARATUS FOR LOGGING DRILL HOLES LyleDillon, San Gabriel, Calif., assignor to Union Oil Company ofCalifornia, Los Angeles, Calii., a corporation of California Originalapplication August 28, 1936, Serial No. 98,355. Divided andthisapplication June 5, 1943, Serial No. 489,769

14 Claims; (01. 177-352) This invention relates to drill hole testingand particularly to electrical and acoustical methods and apparatus forthe determination of the stratigraphy of earth bore holes such as oilwells. This application is a division of my earlier application, SerialNo. 98,355, filed August 28, 1936.

The primary object of this inventionis to provide a method and apparatusby which subsurface measurements of bore hole stratigraphy, pressure,temperature, inclination and the like can be made within the depths ofthe bore hole and by which these measurements can be continuouslytransmitted to the ground surface without the necessity of employingexpensive and troublesome electrical connecting cables.

The broad invention accordingly resides in a method and apparatus formaking physical measurements such as formation and fluid temperatures,pressures and electrical properties and bore-hole inclinations withinthe depths of a bore hole, transforming the measurements into mechanicalvibrations which are proportional to or indicative in character of thesaid measurements, transmitting these vibrations mechanically throughthe fluid in the bore hole or through the supporting cable or throughthe surrounding form'ations to the earth surface, detecting andamplifying these vibrations at the surface and ascertaining or recordingthe said measurements in accordance with the character of the thusoriginated and detected vibrations. The invention resides morespecifically in a method and apparatus for measuring the electricalcharacteristics of the unitary portions of the penetrated formationstrata within the depths of a bore hole such as an oil well,transferring these measurements into mechanical vibrations, thefrequencies of which are functions of the said measurements, detecting,amplifying and measuring these mechanical vibrational frequenciesreceived at the earth surface and determining therefrom thecorresponding electrical measurement made within the bore hole.

Other objects and novel features of the invention will be evidenthereinafter.

In the drawings, wherein typical embodiments of the invention are hownby way of illustration:

Fig. 1 is a diagrammatic sectional elevation of a well bore hole showingthe general arrangement of the apparatus. Fig. 2 is an enlargedelevation of the portion of the apparatus which is lowered into the borehole, diagrammatically illustrating the apparatus and electricalcircuits enclosed therein. Fig. 3 diagrammatically illustrates anoptional arrangement of the enclosed apparatus I and electrical circuitsof Fig. 2. Fig. 4 shows a' ture-operated device which may be optionallysubstituted for the galvanometer G of Fig. 2

when bore-hole temperature readings are made.

Fig. 7 diagrammatically illustrates a gravity-operated device which maybe substituted for the galvanometer G in Fig. 2 when bore-holeinclination determinations are made.

The apparatus is as follows:

Referring to Fig. 1, W is an instrument adapted to be lowered by anappropriate steel line or cable l0 into the earth bore hole I l. M is anelectrical pickup device such as a crystal, magnetic, condenser orcarbon microphone, geophone or the like device adapted to transformmechanical or seismic vibrations into fluctuating electrical currents ofcorresponding character or frequency. A represents an amplifier of theconventional vac-' uum tube design capable of great sensitivity andpreferably selective or'tunable over the range of frequencies employed.The frequency meter F is adapted to receive and indicate the frequenciesor changes of frequencies of the amplified current from the amplifier A.a

The instrument W which is that portion of the apparatus adapted to belowered into the bore hole, comprises a liquid-tight metal cylindricalcontainer l2 enclosing the electrical apparatus diagrammaticallyillustrated within the dotted enclosure |5 in Fig. 2, and alsoconstitutes one electrode of the electrical bore hole testing system.

Projecting from the lower end of the cylinder l2 and rigidly attachedthereto by means of a coaxial, hollow insulating rod l4 through whichconductor 50 extends, is another short metal cylinder I 2a constitutinga lower electrode.

At the upper end of the metal cylinder l2 above the compartment whichhold the hereinbefore mentioned electrical apparatus, ispositioned thevibration producing means which by way of illustration as in Fig. 4comprises a piezoelectric crystal 20 adapted to be electricallyenergized by means of an alternating electricpotential which is imposedbetween the lower heavy cylindrical electrode 2| and the upper lightring electrode 22. The lower cylindrical electrode 2| is coaxiallysupported within the upper section of the cylinder l2 and electricallyinsulated therefrom by means of rigid insulating material 23 such asBakelite. The contact surfaces between the electrode 2|,

within the circular recess 24 at the top of the insulating body 23. Thering electrode 22 rests lightly upon the top surface of thepiezoelectric crystal 24 and is retained in place and electricallygrounded to the instrument body by means of spring connection 25 andconductor 46. A short distance above the top surface of thepiezoelectric crystal 20 is a flexible corrugated metal diaphragm 21making a liquid-tight division between the inner and outer portions ofthe upper section of the metal cylinder. The metal diaphragm 21 isclamped and held in liquid-tight contact with the upper end of the metalcylinder l2 by means of threads 28 and the perforated collar 29. Thespace 33 intermediate the top of the insulating body 23 and thepiezoelectric crystal 20 and the bottom surface of the metal diaphragm21 is entirely filled with an insulating oil of low viscosity.

The perforated collar 29 shown in Fig. 4 is open at the top and alsocarries a plurality of holes forming additional lateral passageways fromthe top of the diaphragm to the outside. At the top of the collar 29 isprovided an open topped threaded connection 3! to which the supportingbail 32 is attached. Upon lowering the instrument into the well, fluidtherein is free to flow around the bail into the top and through theholes 39 of the collar 29. The upper surface of the metal diaphragm 21is thus in physical contact with the drilling fluid in the bore hole andvibrations originated by the piezoelectric crystal are free to passupward through the oil through the metal diaphragm 21 and directlyupward past the ball 32 or outwardly through the holes 30 into thedrilling fluid contained in and surrounding the upper'section of theinstrument. The holes 30 in the collar 29 are provided to allow lateralpassage as well as vertical passage of the vibrations into the drillingfluid withinthe bore hole, and to minimize accumulation of sand andcuttings upon the top of the metal diaphragm 21.

Wheatstone bridge with a low frequency alter nating current source 40connected across two legs thereof and an alternating current galvanom-.As the instrument is lowered into the fluid in the bore hole, thehydrostatic pressure of the drilling mud or other fluid in the wellbears upon the metal diaphragm-21 and the resulting force is transferredin turn through the oil and through the insulating body 23 to thesupporting lugs 26. The electrode 2l is electrically connected to theapparatus within the shell through rod 84 which makes liquid-tightcontact through the insulating body 29.

In Fig. 5 is shown an optional arrangement of the mechanism within theupper end of the cylinder I: of the apparatus W. Here the arrangement ofthe piezoelectric crystal and its associated electrodes aresubstantially the same as that described'hereinabove, but instead ofsupporting the cylinder by means of the steel line connection to the topof the bail-32 the steel line ll enters the top of the instrument and isattached to a metal disk 35 which is in turn solidly imbedded in anelastic rubber body I. This rubber body is flexibly held under pressurewithin the top of the cylinder so as to transfer the weightof theinstrument to the steel line |l through the threaded ring nut 21. Thiselastic rubber body it rests under compression in solid contact upon theupper surface of the metal diaphragm 21, and vibrations originating atthe piezoelectric crystal 24 will be eter G connected across theopposite two legs thereof. The alternating current supply is of such lowfrequency that inductance and capacitive effects of the bridge circuit,associated electrical connections and formation are negligible, thereversal of the current serving only to prevent undesirable electrodepolarizing effects. sistances R1 and R2 may ordinarily be of equalvalue. Variable resistance R0 is employed for obtaining a balancingadjustment of the bridge circuit. Two legs of the Wheatstone bridgecircuit are connected through conductors 49 and 50 across the electrodesl2 and l2a. I

The galvanometer G carries upon the end of its moving arm 4|, which is astrip of insulating material, a metal plate 42. Adjacent the metal plate42 is a stationary metal plate 43 of similar size, the two plates 42 and43 constituting the opposite elements of a variable capacity. Theseelements 42 and 43 are connected in shunt to an inductance winding Lwhich in turn constitutes the frequency control portion of aconventional self-oscillating vacuum tube circuit. Such selfoscillatingvacuum tube circuits are well understood and for this reason theapparatus and operation of the vacuum tube oscillator will not bedescribed in detail except to indicate that the piezoelectric crystal 20is connected to the plate output circuit thereof between electrodes 21and 22 by means of electrical conductors 45 and 46. Inductances 41 and48 serve to prevent the alternating component of the plate outputcurrent from being shortcircuited through the plate voltage supplybatteries.

Fig, 3, as stated hereinabove, illustrates an optional arrangement ofthe apparatus enclosed within the dotted rectangular enclosure l5. Herethe conventional self-oscillating vacuum tube circuit is retained asbefore, but the inductance L is connected through the series condenser44 directly in shunt to the electrodes l2 and Ho by means of theconductors 49 and 50 respectively. This circuit is thus adapted tomeasure directly variations in the dielectric properties of unitaryportions or penetrated formations surrounding the bore hole and adjacentthe two said electrodes.

The hereinbefore described electrical pickup device M may be positionedas shown in Fig. 1 either by partial immersion in the drilling fluid atthe top of the bore hole H as shown at 60 or in contact with the earthsurface or liquid within a shallow hole at the earth surface, as shownat ll, or in the case where the mechanical vibrations are transmittedthrough the supporting steel wire II as shown in the arrangement of Fig,5, the pickup device may be connected through suitable linkages to apulley which contacts the 'said steel wire ii in a manner adapted totransfer the longitudinal vibrations through the steel wire to thepickup device as shown at 92. The apparatus for transferring themechanical vibrations fromthe The resteel wire 10 to the electricalpicku device M as shown at 62 may comprise three pulleys making contactwith the wire line and staggered as shown so as to produce a slightlyangular deflection between the two outermost pulleys. Tension is thusapplied against the middle pulley 63 from which the vibrations aretransmitted through the linkage 64 to the said pickup device M.Electrical connection is made between the pickup device M to theamplifier A through a pair of conductors 61. The amplifier A is in turnconnected to the frequency meter through'a pair of electrical conductors88.

The operation is as follows, considering first the apparatus as shown inFigs 1, 2 and 4: Prior to lowering the well testing apparatus comprisingthe cylinders l2 and We into the fluid-filled bore hole, the resistanceR in the Wheatstone bridge B of Fig. 2 is adjusted to such a value thatfor all the changes of measured formation resistivities, the range ofmotion of the galvanometer G, due to the resulting unbalance of theWheatstone bridge, will be suitable. This adjustment may be ascertainedby preliminary test runs in an artificial bore hole containing drillingmud of the type employed in the well to be tested or by shortpreliminary runs within the actual bore hole to be tested. As thetesting apparatus is lowered into the bore hole and the metal surfacesof the cylinders I2 and I2a which constitute the testing electrodes passadjacent the edges of penetrated strata, the variations in resistancedue to the different resistivities of the adjacent formations uponmotion of the apparatus through the bore hole results in a balancing orunbalancing of the Wheatstone bridge B dependin upon thebefore-mentioned adjustment of resistance R0. The resultant motion ofthe elements of the galvanometer G causes motion of the condenser plate42 relative to'the opposite condenser plate 43. This relative motion ofthe condenser plate 42 will thus be a function of the changes ofresistivities of the formations which are brought adjacent to the saidelectrode surfaces l2 and 12a of the testing apparatus during its motionthroughout the length of the bore hole. Since these condenser plates 42and 43 are electrically connected in shunt to the inductance L, whichcombination comprises the frequency control circuit of theself-oscillatory vacuum tube circuit, the frequency of the outputelectrical current therefrom will be varied in accordance with thefunction of the said resistivity changes.

The alternating current output of the thus controlled vacuum tubeoscillatory circuit is impressed through the connecting conductors 45and 46 upon the piezoelectric crystal 20 which lies between theelectrodes 2| and 22. Since it is the property of a piezoelectriccrystal to change its linear dimensions in accordance with a functionof" the impressed electric potential upon its surfaces, thepiezoelectric crystal 20 will be set into vibration'at a frequencycorresponding to that of the output of the vacuum tube oscillatorycircuit. The piezoelectric crystal thus set into vibration transfersthese vibrations to the surrounding material which, in the present case,as illustrated in Fig. 4, comprises the oil, the metal diaphragm 21, thedrilling fluid within the collar 29 below the bail 32 and thence to thedrilling fluid column within the drill hole and to the surroundingformation in succession.

The vibrations thus transferred to the drilling fluid within the holeand the surrounding formation will be transmitted upwardly to the earthsurface where they are received by means of the electrical pickupdevices M placed either at the surface of the drilling fluid shown at 60or upon the earth surface as shown at 6|. When employing thepiezoelectric crystal pickup device or crystal microphone, the processis in reverse to that employed for generating the vibrations at theinstrument within the bore hole. That is, the earth or mud vibrationsare received and transferred to the piezoelectric crystal surfaces asvibrational pressure changes resulting in corresponding fluctuatingpotentials to be generated upon these crystal surfaces and these smallpotential difference fluctuations are then transferred through theconductor 61 to the amplifier A where a greatly magnified alternatingcurrent of corresponding characteristic is generated. y

This greatly magnified alternating current is v conducted through 68' tothe frequency meter F which is capable ofdiscriminating between thedifferent frequency characteristics of the thus amplified current. Thefrequency meter F may be of any of the well known types such as forexample one similar to that commonly employed for measuring highfrequency electrical currents such as the wave meter. Such a frequencymeter generaliy comprises an electrical oscillatory circuit of variablenatural frequency characteristics and means such as a galvanome'ter toindicate resonant conditions. The frequency characteristics of such anapparatus are generally varied by means of a variable capacity. Such afrequency measuring device may be here employed and if desired thevariable capacity adjustment for determining the condition of resonancemay be directly calibrated in terms of resistivity measurements withinthe bore hole.

- vacuum tube oscillatory circuit.

Other measurements besides resistivity within a bore hole are desirable,however, as stated before. For example, the dielectric characteristicsof the surrounding formations within a bore hole can be measured. Whensuch dielectric measurements are to be made the electrical apparatusdiagrammatically shown within the dotted enclosure !5 of Fig. 3 issubstituted for that of Fig. 2. In this case the inductance L isdirectly connected through the condenser 44 and through the conductors49 and 50 to the cylindrical metal electrode surfaces l2 and I211. Thesurfaces l2 and l2a thus actas plates of a condenser, the capacity ofwhich is in shunt to the inductance L of the thermionic vacuum tubeoscillatory circuit, and they are charged by the oscillatory currentgen- .erated thereby. Sinc the current by which the electrodes I2 andl2a are thus directly energized is of high frequency, the effects of thepresence of adjacent formations upon the effective capacity between theelectrodes I 2 and l2a and across the inductances L, is thatpredominantly due to their dielectric properties.

The portion of the penetrated formations adjacently extending betwen theelectrode surfaces 1 2 and I20, andincluded in the electric fieldtherebetween, constitutes that elementary formation unit which is testedfor each given instrument position within the bore hole. Dotted line l3indicates the approximate path of the electric field through theformation.

I Changes in dielectric properties of adjacent formations during motionof the testing apparatus within the bore hole, therefore, effects achange in the capacity across the inductance L and thereby changes thefrequency of oscillation ofthe This variable frequency electrical outputof the vacuum tube- 7 circuit is in turn impressed upon thepiezoelectric crystal and the resulting vibrations transmitted to theearth surface as described hereinabove in connection with Figs. 1, 2 and4. By

moving the instrument through the bore hole a continuous record ofchanges in dielectric properties throughout any desired length thereofis obtained.

In Fig. 5, instead of directly transferring the crystal vibrations tothe drilling fluid at the top of the testing apparatus as describedhereinbefore, these vibrations are transferred from the piezoelectriccrystal 20 through the oil. the metal diaphragm 21 and the rubber 36 tothe metal disk 35 and thence as longitudinal vibrations through thesteel supporting cable ID to the ground surface. The vibrations thustransferred to the steel supporting cable [0 are picked up andtransformed to 8 as the method for" generating the mechanical vibrationswithin the bore hole. other well known means are obviously applicable tothe circuits described and illustrated herein. For example, the wellknowndynamic oscillator or vibrator comprising an electrical circuit inan intense electromagnetic field such as employed for subelectricalimpulses by means of the pickup device M at 82, the vibrations beingtransferred as before described from the cable through the pulley 68 andthrough the connecting linkage. 64.

Frequencies employed preferably range from approximately 10,000 to100,000 vibrations per second, the frequencies preferably being aboveaudibility whereby extraneous undesirable noises which might vitiate orinterfere with making the proper readings, are largely eliminated fromthe receiving apparatus. These frequencies from an electrical standpointare relatively low and therefore large values of inductance and capacityin the variable electrical circuits by which the transmitting vibrationsare generated are necessary. For this reason it is sometimes desirableto employ means not only to vary the capacities but also to vary theinductances of the'oscillatory circuits as well. Such a variation of alarge inductance may be accomplished by appropriately controlled,variable electromagnetic circuits associated with the inductances.

Other'measurements which may be made within the bore hole utilizingapparatus similar to that illustrated in Fig. 2 are temperature,pressure, and bore hole inclination.

When fluid temperature measurements are made within the bore hole atemperatureoperated devic such as a bimetal element thermometer issubstituted for the galyanometer shown in Fig. 2. The capacity of thesystem comprising the two plates 42 and 43 is by this means varied inaccordance with changes of temperature. The thermometer is preferablyplaced in the instrument in a position to readily partake of thetemperature of the surrounding drilling fluid and formations.

When it is desired to measure the inclination of the bore hole apendulum-operated device such as illustrated in Fig. 7 is likewisesubstituted for the galvanometer G and the movable plates ll and 42 inFig. 2 whereby variations in deviations from the vertical of the borehole in which the instrument is lowered, activates a variation indistance and hence the capacity between the pendulum element Ill and thering H and. thus varies the frequency of the vacuum tube oscillatorcircuit ashereinbefore described. The pendulum 10 is universallypivotedat 12 so that it is free to remain in a vertical position within theinstrument W while the ring Ii is rigidly supported in a. fixed positiontherein. Deviation of the instrument from the perpendicular will thuscause the pendulum element 10 to move toward the ring II reducing theelectrical capacity therebetween as just stated.

While piezoelectric means has been disclosed marine signaling may beemployed.

While only a single stage thermionic vacuum tube oscillator isillustrated herein, additional stages of amplification may obviously beemployed to obtain a greater intensity of crystal or vibratorexcitation.

Instead of employ ng continuous vibrations which are controlled infrequency according to a function of the measurements to be made withinthe bore hole, intermittent vibrations may be employed, the timeinterval of which is similarly a function of the desired measures.Vibrations in the audible frequency range can also be employed.

The foregoing is merely illustrative of the method and apparatus of theinvention and is surface comprising varying the characteristics of anelectric current in accordance with said resistlvities, converting saidelectric current into mechanical vibrations of a character correspondingto the character of said current and detecting and receiving saidvibrations at the earth surface whereby the resistivities of the unitaryportions of penetrated formations surrounding the bore hole may bedetermined.

2. A method for transmitting resistivity instrument readings from withina bore hole to the surface comprising varying the characteristics of anelectric current in accordance with a function of the resistivityinstrument reading in the bore hole, converting mid. current intomechanical vibrations corresponding to the character of said current,and detecting and amplifying said vibrations at the surface whereby theresistivity instrument reading within the bore hole may be determined. 1

3. A method of transmitting resistivity measurements from within a borehole to the earth surface comprising varying the characteristics of anelectriccurrent in accordance with a function of the said resistivitymeasurements in the bore current, transferring said vibrations to theearth formations surrounding the bore hole whereby the said vibrationsare transmitted through the formations to the earth surface anddetecting and measuring the character of the said vibrations thustransmitted to the earth surface whereby the resistivity measurementwithin the bore hole may be ascertained.

4. A method for transmitting indications of resistivities of the unitaryportions of penetrated formations surrounding a bore hole to the earth'ssurface comprising generating mechanical vibrations in the bore hole,controlling the frequency of said vibrations in accordance with a knownfunction of said resistivities,- transmitting said vibrations fromwithin the bore hole to the earth's surface, detecting said vibrationsat the earth's surface and measuring the frequency of said detectedvibrations whereby the resistivities of the unitary portions ofpenetrated formations surrounding the bore hole may be determined.

5. A method of logging resistivities of the uni-' tary portions ofpenetrated formations surrounding a bore hole comprising varying thefrequency of an alternating electrical current in accordance with afunction of the resistivity of a unitary portion of the formationsurrounding the bore hole, converting said alternating current intomechanical vibrations of a corresponding frequency within the bore holewhereby said mechanical vibrations are transmitted into and through thesurrounding earth formations and whereby a portion of the vibrationalenergy reaches the earth surface, and detecting and measuring thefrequency of the mechanical vibrations at the earth surface whereby theresistivities of the said unitary portions of the formation may bedetermined.

6. A method of logging resistivites of the unitary portions ofpenetrated formations surrounding a bore hole comprising lowering aninstrument which is sensitive to resistivities of unitary portions'ofthe surrounding formations through the borehole, generating mechanicalvibrations within the instrument in the bore hole, controlling thecharacter of said generated vibrations by said instrument in accordancewith a function of the said changes of the resistivities of the unitaryportions of the surrounding formations as the instrument moves throughthe bore hole, transferring said mechanical vibrations whereby a portionof the vibrational energy reaches the earth surface and detecting andmeasuring the changes of the character of the mechanical vibrations atthe earth surface which vibrations correspond to the said function ofthe changes of the resistivities of the tions surrounding the bore hole.

7. A method of logging resistivities of unitary portions of penetratedformations surrounding a bore hole comprising lowering on a supportingline an instrument which is sensitive to resistivities of unitaryportions of the surrounding formations through the bore hole, generatingmechanical vibrations within the said instrument in the bore hole,controlling the character of said generated vibrations bi saidinstrument in accordance with a functi n of the changes of theresistivitles of the unitary portions of the surrounding formations asthe instrument moves through the bore hole, transferring said mechanicalvibrations to the supporting line whereby a portion of the vibrationsare transmitted longitudinally through the said line to the earthsurface, detecting and measuring the changes of the character of thesaid vibrations arriving at the earth surface through the saidsupporting line which vibration changes also correspond in character tothe said function of the changes of the resistivitles of the unitaryportions of the formations surrounding the bore hole.

8. A method for transmitting indications of the resistivities of theformations surrounding a bore hole to the earth surface comprisinggenerating mechanical vibrations in the bore hole of a character whichis a function of said resistivities of the unitary portions of thepenetrated formations surrounding the bore hole, transmitting saidvibrations from within the bore hole to the earth surface and detectingsaid vibrations at the earth surface unitary portions of theformaunitary portions of penetrated the desired resistivity data.

of penetrated formations surrounding the bore function of the saidresistivities of the unitary portions of the penetrated formationssurrounding the bore hole to be measured, means to generate mechanicalvibrations corresponding in frequency with said alternating current, andmeans to transmit'said mechanical vibrations to the earth surface.

10. Apparatus according to claim 9 in which the means to transmit themechanical vibrations to the earth surface comprise a line by which theinstrument is lowered into the well bore hole.

11. Apparatus for transmitting indications of the resistivities ofunitary portions of the Danetrated formations surrounding the bore holecomprising an instrument adapted to be lowered into a well bore hole,said instrument comprising a thermionic vacuum tube oscillator, means tovary the frequency of the electrical oscillations of said oscillator inaccordance with a function of the variations of resistivities of unitaryportions of the penetrated formations surrounding the bore hole as theinstrument moves therethrough. electrical means to transform the thusgenerated and controlled electrical oscillations into mechanicalvibrations of corresponding frequency, means to transmit said mechanicalvibrations from said instrument in the bore hole to the earth surfaceand a microphone at the earth surface to receive and transform thevibrations into an alternating current of corresponding frequency, meansto amplify said alternating current from the microphone, and meanscapable of indicating changes in said amplified alternating currentfrequency.

12. A method according to claim 4 in which the said generated mechanicalvibrations are supersonic.

13. Method of transmitting resistivity data from a sub-surfaceprospecting instrument to surface apparatus that comprises creating, anelectrical oscillation at the prospecting instrument, altering saidoscillation in accordance with resistivity data from said instrument,translating the electrical oscillation into mechanical vibrations,transmitting. the vibrations to the surface, analyzing the vibrations atthe surface to obtain and operating the indicating apparatus inaccordance therewith.

14. Method of transmitting datasfrom a s'uband operating the indicatingapparatus in accordance therewith.

. LYLE DILDON.

.whereby the resistivities of the unitary portions

